New webpage on loudspeaker cables
 

On Mon, 10 Aug 2009 15:30:02 +0100, "David Looser"
wrote:

"Ian Iveson" wrote in message
...

One problem of being at the end of science is that the devil
makes work for idle minds. If you really have nothing to
write about, stop writing. Integrity is perishable. Your
magazine will be lucky to survive as it is, without you
taking the **** out of its readers.


What an extraordinary post! You clearly haven't understood a word of any
what Jim has been and are trying to cover up your ignorance with a load of
sarcasm. It doesn't wash.

I was just thinking the same.

d

New webpage on loudspeaker cables
 

In article , Ian Iveson
wrote:
Jim Lesurf wrote:

Thank heavens for Hi Fi News.

Of course I rushed out to buy my wonderful Isolda cables immediately.
With the old Maplin leads, *anything* might have been happening.
After all, some amplifiers have some problems with some other cables,
and since we don't know which amplifiers, or what problems, or which
cables, it's better to be on the safe side.

Shame you didn't read the above article with more care.

Left to right, top to bottom, line by line. How much care does reading
need?

Erm.. I think it may require that you employ your mind as well as your eye
muscles. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

On Sat, 08 Aug 2009 09:46:15 +0100, Jim Lesurf wrote:

In article , mick
wrote:
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:




I'm unsure about drawing any conclusions from graphs that start at 5x
the accepted maximum audible frequency. I hope Jim has included tests
on VHF coax as speaker leads too - it makes as much sense to me...
;-)

The problem is that some amplifier designs can be upset by having a load
at RF which does not suit them. The classical symptom is either
sustained oscillations in the region around a MHz or above, or bursts of
oscillations with particular audio waveforms. This can alter the audio
behaviour. The effects are measurable as well as audible.

Alas, the amplifier designer has no control over what loads the user
connects. And this will change with the choice and length of the
loudspeaker cables.



Fair enough, but surely the only amps that are likely to have much output
(i.e. enough to drive the cable - never mind the speaker) above 1MHz or
so are likely to have severe problems anyway (such as overheating) aren't
they? Ok, maybe not if the oscillations are triggered on audio peaks I
suppose, but how would that be audible?


*If* your amp has much output above 100kHz then it is faulty and needs
looking at - seriously.

I agree. However some commercial amps *have* produced oscillations like
this with some loadings. For all I know, some still do.

And one of the points of the RF measurements is that it allows you to
determine the cable properties which you can then apply at audio
frequencies to assess what changes may occur *in* the audio band even
when the amplifier is stable and happy. So the measurements are useful -
if you understand why they were made and how to use the results. :-)



I'm still trying to get the hang of this - please excuse my stupidity and
put it down to old age! Ok, cable always influences RF performance, I'm
happy with that. I'm incredibly skeptical about whether it affects
audible results though. The L, C and R and/or Z values are just too low
at audible frequencies. This is demonstrated on your graphs, where at
500kHz there is virtually nothing to differentiate one cable from
another, no matter what the cost. AFAIK even the advocates of extended
frequency response can't hear harmonics up there. :-)

Now I have to get around getting enough RF out of an audio amp to make
those values important. At the frequencies you are talking about a simple
zobel, or even a 1nF capacitor across the output should remove enough RF
to swamp the effects. Values are probably very uncritical. Obviously if
the amp has nothing across the output then there will probably be
problems, but how often does that happen when the components are so
cheap?

I'm not convinced that knowing the RF cable properties tells you anything
at all about the audio performance. There shouldn't be any RF present so
the information is redundant. It may tell you whether to expect the
leakage of magic smoke if you connect an unstable amp to a measured cable
though... ;-)

I'd be interested to see measurements for a bit of mains twin and earth,
if the mood to test takes you again... :-D

All very educational. Thanks, Jim. :-)

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

New webpage on loudspeaker cables
 

In article , David Looser
wrote:
"Ian Iveson" wrote in message
...

One problem of being at the end of science is that the devil makes
work for idle minds. If you really have nothing to write about, stop
writing. Integrity is perishable. Your magazine will be lucky to
survive as it is, without you taking the **** out of its readers.


What an extraordinary post! You clearly haven't understood a word of any
what Jim has been and are trying to cover up your ignorance with a load
of sarcasm. It doesn't wash.

That may be be a result of his assuming that scanning his eyes is all that
is needed to actually understand what was written. But since this is usenet
I guess it is more likely that he just wanted to grab a chance to argue
without having to bother with the minor detail of understanding what he had
read sic first. My troll detector did buzz when I read his posting. I
suspect his follow on postings will clarify that. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

New webpage on loudspeaker cables
 

On 10 Aug 2009 15:30:16 GMT, mick wrote:

On Sat, 08 Aug 2009 09:46:15 +0100, Jim Lesurf wrote:

In article , mick
wrote:
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:




I'm unsure about drawing any conclusions from graphs that start at 5x
the accepted maximum audible frequency. I hope Jim has included tests
on VHF coax as speaker leads too - it makes as much sense to me...
;-)

The problem is that some amplifier designs can be upset by having a load
at RF which does not suit them. The classical symptom is either
sustained oscillations in the region around a MHz or above, or bursts of
oscillations with particular audio waveforms. This can alter the audio
behaviour. The effects are measurable as well as audible.

Alas, the amplifier designer has no control over what loads the user
connects. And this will change with the choice and length of the
loudspeaker cables.



Fair enough, but surely the only amps that are likely to have much output
(i.e. enough to drive the cable - never mind the speaker) above 1MHz or
so are likely to have severe problems anyway (such as overheating) aren't
they? Ok, maybe not if the oscillations are triggered on audio peaks I
suppose, but how would that be audible?


*If* your amp has much output above 100kHz then it is faulty and needs
looking at - seriously.

I agree. However some commercial amps *have* produced oscillations like
this with some loadings. For all I know, some still do.

And one of the points of the RF measurements is that it allows you to
determine the cable properties which you can then apply at audio
frequencies to assess what changes may occur *in* the audio band even
when the amplifier is stable and happy. So the measurements are useful -
if you understand why they were made and how to use the results. :-)



I'm still trying to get the hang of this - please excuse my stupidity and
put it down to old age! Ok, cable always influences RF performance, I'm
happy with that. I'm incredibly skeptical about whether it affects
audible results though. The L, C and R and/or Z values are just too low
at audible frequencies. This is demonstrated on your graphs, where at
500kHz there is virtually nothing to differentiate one cable from
another, no matter what the cost. AFAIK even the advocates of extended
frequency response can't hear harmonics up there. :-)

Now I have to get around getting enough RF out of an audio amp to make
those values important. At the frequencies you are talking about a simple
zobel, or even a 1nF capacitor across the output should remove enough RF
to swamp the effects. Values are probably very uncritical. Obviously if
the amp has nothing across the output then there will probably be
problems, but how often does that happen when the components are so
cheap?

I'm not convinced that knowing the RF cable properties tells you anything
at all about the audio performance. There shouldn't be any RF present so
the information is redundant. It may tell you whether to expect the
leakage of magic smoke if you connect an unstable amp to a measured cable
though... ;-)

I'd be interested to see measurements for a bit of mains twin and earth,
if the mood to test takes you again... :-D

All very educational. Thanks, Jim. :-)

Provided the amplifier is not made unstable by the particular RF load
of the cable, it will make no difference to the sound.

But when an oscillation happens, the result can be severe. Frequently
the oscillation only occurs over a small part of the waveform, but
when it does, like any oscillator, the amplifier is driven instantly
into saturation. That results in something like clipping of the audio
waveform, which is definitely audible.

When you have only audio test equipment - oscilloscopes etc - the
effect can be very hard to identify. It might be a barely visible
wiggle towards the top of a sine wave. It generally won't be found
when doing a distortion measurement, because when you do that, you run
into a nice resistive load. It only happens into a speaker type load
and the audio-only designer will never find it. Frequently the only
clue is an output device that seems to run a little hotter than it
should.

So here's the thing. For the consumer, knowing the impedance of a
cable is not important, although it is clear from Jim's work that you
are less likely to run into trouble with some than others. But the
article should be a wake-up call to anyone in the design business that
a blinkered, audio-limited view can be a recipe for a very poor
amplifier, whatever the measurements may say.

d

New webpage on loudspeaker cables
 

"David Loser is a ****WIT "

"Ian Iveson"

One problem of being at the end of science is that the devil
makes work for idle minds. If you really have nothing to
write about, stop writing. Integrity is perishable. Your
magazine will be lucky to survive as it is, without you
taking the **** out of its readers.


What an extraordinary post!


** Indeed - rarely has Iveson ever been so insightful.

The DEVIL does indeed make work for idle minds, be they criminally
inclined ones at one end of the scale OR just totally off with the
scientific pixies at the other.

Like JL is.


You clearly haven't understood a word of any what Jim has been ...

** Huh ???

JL has not actually said a thing that can be understood

- unless YOU are off dancing with the same pixies he does..


and are trying to cover up your ignorance with a load of sarcasm. It
doesn't wash.


** Try washing some of that smug bull**** out of your head

- you pig ignorant pommy arsehole.




...... Phil

New webpage on loudspeaker cables
 

"mick" wrote

Fair enough, but surely the only amps that are likely to have much output
(i.e. enough to drive the cable - never mind the speaker) above 1MHz or
so are likely to have severe problems anyway (such as overheating) aren't
they? Ok, maybe not if the oscillations are triggered on audio peaks I
suppose, but how would that be audible?

Because it causes distortions *within* the audio band.


I'm still trying to get the hang of this - please excuse my stupidity and
put it down to old age! Ok, cable always influences RF performance, I'm
happy with that. I'm incredibly skeptical about whether it affects
audible results though. The L, C and R and/or Z values are just too low
at audible frequencies. This is demonstrated on your graphs, where at
500kHz there is virtually nothing to differentiate one cable from
another, no matter what the cost. AFAIK even the advocates of extended
frequency response can't hear harmonics up there. :-)

See above. The whole point of this is that instability can result way out of
the audio band, but that can result in distortion within the audio band.

Now I have to get around getting enough RF out of an audio amp to make
those values important. At the frequencies you are talking about a simple
zobel, or even a 1nF capacitor across the output should remove enough RF
to swamp the effects.

Arggh!... Plonking a 1nF capacitor across the output of a feedback amplifier
is a pretty likely way of making it unstable

I'm not convinced that knowing the RF cable properties tells you anything
at all about the audio performance.

Nor am I. AFAIAC the whole thing is about stability, and how likely the
cable is to provoke oscillation in amplifiers with marginal stability.

There shouldn't be any RF present

Ideally there wouldn't. But what makes you think that there isn't?. With
active devices having good gain up into the hundreds of megahertz what makes
you think there isn't noise, RF pickup and self-oscillation well above the
audio band present?

David.

New webpage on loudspeaker cables
 

"Phil Allison" wrote in message
...


JL has not actually said a thing that can be understood


Not by you obviously. But then not everyone is as ignorant as you are.

David.

New webpage on loudspeaker cables
 

On Mon, 10 Aug 2009 15:40:39 +0000, Don Pearce wrote:

snip

Provided the amplifier is not made unstable by the particular RF load of
the cable, it will make no difference to the sound.

But when an oscillation happens, the result can be severe. Frequently
the oscillation only occurs over a small part of the waveform, but when
it does, like any oscillator, the amplifier is driven instantly into
saturation. That results in something like clipping of the audio
waveform, which is definitely audible.

When you have only audio test equipment - oscilloscopes etc - the effect
can be very hard to identify. It might be a barely visible wiggle
towards the top of a sine wave. It generally won't be found when doing a
distortion measurement, because when you do that, you run into a nice
resistive load. It only happens into a speaker type load and the
audio-only designer will never find it. Frequently the only clue is an
output device that seems to run a little hotter than it should.

So here's the thing. For the consumer, knowing the impedance of a cable
is not important, although it is clear from Jim's work that you are less
likely to run into trouble with some than others. But the article should
be a wake-up call to anyone in the design business that a blinkered,
audio-limited view can be a recipe for a very poor amplifier, whatever
the measurements may say.



Thanks - that's the sort of info I was looking for. :-)

--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

New webpage on loudspeaker cables
 

Don Pearce wrote:
On 10 Aug 2009 15:30:16 GMT, mick wrote:

On Sat, 08 Aug 2009 09:46:15 +0100, Jim Lesurf wrote:

In article , mick
wrote:
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:

I'm unsure about drawing any conclusions from graphs that start at 5x
the accepted maximum audible frequency. I hope Jim has included tests
on VHF coax as speaker leads too - it makes as much sense to me...
;-)
The problem is that some amplifier designs can be upset by having a load
at RF which does not suit them. The classical symptom is either
sustained oscillations in the region around a MHz or above, or bursts of
oscillations with particular audio waveforms. This can alter the audio
behaviour. The effects are measurable as well as audible.

Alas, the amplifier designer has no control over what loads the user
connects. And this will change with the choice and length of the
loudspeaker cables.


Fair enough, but surely the only amps that are likely to have much output
(i.e. enough to drive the cable - never mind the speaker) above 1MHz or
so are likely to have severe problems anyway (such as overheating) aren't
they? Ok, maybe not if the oscillations are triggered on audio peaks I
suppose, but how would that be audible?


*If* your amp has much output above 100kHz then it is faulty and needs
looking at - seriously.
I agree. However some commercial amps *have* produced oscillations like
this with some loadings. For all I know, some still do.

And one of the points of the RF measurements is that it allows you to
determine the cable properties which you can then apply at audio
frequencies to assess what changes may occur *in* the audio band even
when the amplifier is stable and happy. So the measurements are useful -
if you understand why they were made and how to use the results. :-)


I'm still trying to get the hang of this - please excuse my stupidity and
put it down to old age! Ok, cable always influences RF performance, I'm
happy with that. I'm incredibly skeptical about whether it affects
audible results though. The L, C and R and/or Z values are just too low
at audible frequencies. This is demonstrated on your graphs, where at
500kHz there is virtually nothing to differentiate one cable from
another, no matter what the cost. AFAIK even the advocates of extended
frequency response can't hear harmonics up there. :-)

Now I have to get around getting enough RF out of an audio amp to make
those values important. At the frequencies you are talking about a simple
zobel, or even a 1nF capacitor across the output should remove enough RF
to swamp the effects. Values are probably very uncritical. Obviously if
the amp has nothing across the output then there will probably be
problems, but how often does that happen when the components are so
cheap?

I'm not convinced that knowing the RF cable properties tells you anything
at all about the audio performance. There shouldn't be any RF present so
the information is redundant. It may tell you whether to expect the
leakage of magic smoke if you connect an unstable amp to a measured cable
though... ;-)

I'd be interested to see measurements for a bit of mains twin and earth,
if the mood to test takes you again... :-D

All very educational. Thanks, Jim. :-)

Provided the amplifier is not made unstable by the particular RF load
of the cable, it will make no difference to the sound.

But when an oscillation happens, the result can be severe. Frequently
the oscillation only occurs over a small part of the waveform, but
when it does, like any oscillator, the amplifier is driven instantly
into saturation. That results in something like clipping of the audio
waveform, which is definitely audible.

When you have only audio test equipment - oscilloscopes etc - the
effect can be very hard to identify. It might be a barely visible
wiggle towards the top of a sine wave. It generally won't be found
when doing a distortion measurement, because when you do that, you run
into a nice resistive load. It only happens into a speaker type load
and the audio-only designer will never find it. Frequently the only
clue is an output device that seems to run a little hotter than it
should.

So here's the thing. For the consumer, knowing the impedance of a
cable is not important, although it is clear from Jim's work that you
are less likely to run into trouble with some than others. But the
article should be a wake-up call to anyone in the design business that
a blinkered, audio-limited view can be a recipe for a very poor
amplifier, whatever the measurements may say.

d

That's well put, and notwithstanding Jim's reply to my post earlier (and
thanks), might be a useful sentiment to include in the article/web page?

Rob